Seat belt retracting and winding device

ABSTRACT

The invention relates to a device for automatically retracting and winding up a seat belt for use in a vehicle to protect the occupant and in particular the device controls the force for retracting or winding up the seat belt. The device includes a frame with a winding reel rotatably supported by the frame with spring means connecting the frame and winding reel. The winding reel is adapted to wind thereon a seat belt with a spring force of at least one main and auxiliary springs with a spur gear rotatably supported by the winding reel and operatively interposed between the main and auxiliary springs for changing the winding force and means for detecting a wound quantity of the seat belt.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a device for retracting and winding upautomatically a seat belt used in a vehicle to protect the occupant, andmore particularly to a mechanism for controlling the force forretracting or winding up the seat belt.

2. Description of the Related Art

There have conventionally been known seat belt retracting and windingdevices which contain a winding reel and spring means having one endconnected to the winding reel and the other end connected to a frame ofthe device. This spring means is constituted by two spiral springsconnected to each other through an interposed ratchet means. Thesedevices control the combined spring force of the two springs independence on whether a pawl is engaged with the ratchet means or not,thereby exerting a reduced retracting and winding force to the seat beltafter it has been fastened across the vehicle occupant.

Devices of this type are known from U.S. Pat. No. 4,382,563 entitled"Seat Belt Winding and Retracting Apparatus" and from U.S. Pat. No.4,383,658, entitled "Seat Belt Retracting and Winding Devie". Accordingto the former patent, electromagnetic means selectively actuates thepawl so that the starting condition which a reduced retracting andwinding force is exerted to the seat belt, may adjust in dependence onthe states of the vehicle or physique of the occupant, while theoccupant needs to manually operate a switch for energizing theelectromagnetic actuator means and the reliability in operation isinferior to the latter patent. A disadvantage of the latter patent isthat means for controlling the pawl is complex and difficult to bemanufactured. A further disadvantage of the latter patent is that thestarting condition which a reduced retracting and winding force isexerted to the seat belt, is hardly adjustable in dependence on thestates of the vehicle or physique of the occupant.

SUMMARY OF THE INVENTION

An object of this invention is to provide a seat belt retracting andwinding device in which a reduced retracting and winding force isautomatically exerted to the seat belt after it has been fastened acrossthe vehicle occupant.

Another obJect of the invention is to provide a seat belt retracting andwinding device which is readily manufactured and is reliable inoperation.

Still another object of the invention is to provide a seat beltretracting and winding device in which the starting condition which areduced retracting and winding force is exerted to the seat belt, canadjust in dependeance on the states of a vehicle or physique of theoccupant.

With above objects in view, there is provided according to an aspect ofthis invention a seat belt retracting and winding device which comprisesa winding reel rotatably supported by a frame of the device; springmeans connected between the frame and the winding reel and including amain spring and an auxiliary spring; the winding reel being adapted towind thereon a seat belt with a spring force of at least one of the mainand auxiliary springs; a spur gear rotatably supported by the windingreel and operatively interposed between the main and auxiliary springsfor changing seat belt winding force influenced by the main andauxiliary springs; means for detecting a wound quantity of the seat beltdisposed on the wound seat belt; and a gear for fixing the spur gear andbeing interlocked with the detecting means, the fixing gear beingmounted for movement to releasably engage with the spur gear, thedetecting means being adapted to cause the fixing gear to operateselectively under an engagement condition with said spur gear and adisengagement condition from the spur gear, exerting smaller and largerspring forces, respectively, on the seat belt, whereby the winding forceexerted on the seat belt is reduced when the spring means is operatedunder the engagement condition.

The detecting means preferably includes a drum rotatably and detachablysupported by a shaft of the fixing gear, the drum being adapted to rollon the wound seat belt around the winding reel during its retraction.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other obJects as well as advantages of this invention willbecome more apparent from description of a preferred embodiment of thisinvention with reference to the accompanying drawings, in which:

FIG. 1 is a sectional view taken on line I--I of FIG. 2, illustrating anembodiment of a seat belt retracting and winding device according tothis invention;

FIG. 2 is a cross sectional view taken on line II--II of FIG. 1 withsome parts removed, illustrating the disengagement of a fixing gear froma spur gear when a seat belt is completely retracted and wound on awinding reel; and

FIG. 3 is a partially sectional view similar to FIG. 2, illustrating theengagement of the fixing gear with the spur gear after the seat belt hasbeen fastened.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1, 2 and 3, a frame 10, which is the main body of aseat belt retracting device according to this invention, is formed bythe press operation from a thick steel plate, and has side plates 10aand 10b and a mounting hole 10c for anchoring the frame 10 to the floorof an automotive vehicle. A main shaft 11a of a winding reel 11 isrotatably supported in bush bearings 10d and 10e made of Teflon or thelike and attached to the side plates 10a and 10b. A small shaft 11b isprovided at one end of the main shaft 11a. The reel 11 includes flanges11c and 11d and a spool 11e made integral with the shafts 11a and 11b.The inner end of a seat belt 13 is securely attached to the spool 11ewhile the other end is attached to an anchor or a buckle (not shown).

A case 14, which is molded from suitable synthetic resin, is attached tothe side plate 10b of the frame 10. The case 14 has a cylindricalhousing 14a at the outside thereof in which a spring cover 15 issecured. A cup-shaped spur gear 16 includes a large diameter cylindricalsection 16a and a small-diameter cylindrical section 16b, the latterbeing rotatably supported on the shaft 11b and in a bush bearing 15aattached to a center hole of the spring cover 15. Gear teeth 16c areformed around the outer periphery of the large-diameter section 16a. Oneend 17a of an auxiliary spiral spring 17, which is disposed inside thelarge-diameter section 16a, is fixed to the main shaft 11a (See FIG. 2)while the other end 17b is fixed to the inner wall of the large-diametersection 16a. One end of a main spiral spring 18, which is housed withinthe spring cover 15, is fixed to the small-diameter section 16b whilethe other end is fixed to the inner wall of the spring cover 15 so thatwhen the spur gear 16 is rotated, the main spring 18 is wound around thesmall-diameter section 16b. The spring force of the auxiliary spring 17is weaker than that of the main spring 18.

An intermediate gear 19 engages with the spur gear 16. The intermediategear 19 and a lever 20 are rotatably carried by a shaft 21 fixed at theside plate 10b. The lever 20 has a shaft 22 secured thereto andpenetrating an arc-shaped hole 10f of the side plate 10b (See FIG. 2). Agear 23 for fixing the spur gear 16 is rotatably supported at one end ofthe shaft 22 and engages with the intermediate gear 19. Thus the fixingger 23 can revolve around the intermediate gear 19 whereby the lever 20swings in the hole 10f. A friction washer 24 is carried by the shaft 22between the fixing gear 23 and the lever 20. The fixing gear 23 isadapted to fix the spur gear 16 in engagement therewith where the lever20 swings to the upper end of the hole 10f (See FIG. 3). The lever 20 isadapted to stop at a pin 25 fixed to the side plate 10b where the lever20 swings to the lower end of the hole 10f (See FIG. 2). A drum 26 isrotatably and detachably supported and retained by a ring 27 at theother end (on the side of the reel 11) of the shaft 22. The drum 26 isadapted to roll on the seat belt 13a wound around the spool 11e duringits retraction so as to detect a wound quantity of the seat belt.

In operation, when the seat belt 13 is retracted and wound around thereel 11, the wound belt 13a forces down the drum 26. Because the fixinggear 23 is in disengagement from the spur gear 16, the gears 23, 19 and16 are rotatable so that the belt 13 is completely wound around the reel11 under the combined winding force of the springs 18 and 17 as shown inFIGS. 1 and 2.

As indicated by arrows in FIG. 2, when the occupant pays out the belt13, the latter is unwound from the reel 11 so that the shaft 11a isrotated. As the belt 13 is paid out, the gears 16, 19 and 23 are alsorotated, and both the auxiliary and main springs 17 and 18 are wound.The spring constant of the main spring 18 is larger than that of theauxiliary spring 17 so that first the auxiliary spring 17 is almostwound. After the auxiliary spring 17 has been wound, the rotation in thedirection indicated by the arrow A in FIG. 2 of the shaft 11a istransmitted to the small-diameter section 16b of the spur gear 16through the wound auxiliary spring 17 so that the main spring 18 iswound. Because of the friction washer 24, the lever 20 swings in thedirection B thereby stopping at the pin 25. The position of the pin 25is so selected that when the belt 13 is fully paid out, the drum 26 isin disengagement from the wound belt 13a. Therefore the wound belt 13ais in the position shown in FIG. 3 when the belt 13 is fully paid outand fastened. The drum 26 is changeable for a smaller drum, if the drum26 contacts the wound belt 13a even when the belt 13 is fully paid outand fastened. On the contrary the drum 26 is changeable for a largerdrum.

Thus, when the seat belt 13 is fastened, the unwinding spring force ofthe main spring 18 is exerted to the spur gear 16 in the direction C inFIG. 3 so that the gears 19 and 23 are rotated in the directionindicated by the dotted arrows in FIG. 3, and the lever 20 swings in thedirection D. Consequently, the fixing gear 23 comes to engage with thespur gear 16 thereby fixing it. The fixation of the spur gear 16automatically prevents the unwinding spring force of the main spring 18from transmitting to the shaft 11a. As a result, the tension of the beltis reduced when the belt fastened so that the occupant has less feelingof being restrained.

When the belt 13 is unfastened or released, the shaft 11a is slowlyrotated in the direction E under the unwinding spring force of theauxiliary spring 17. As the belt 13 is wound, the wound quantity of thebelt 13 increases. Therefore the wound belt 13a contacts the drum 26 andlowers the drum 26 and the lever 20. The fixing gear 23 is thereforedisengaged from the teeth 16c of the spur gear 16, so that that spurgear 16 initiates rotation in the direction C under the unwinding springforce of the main spring 18. Then, the rotation of the spur gear 16 isautomatically transmitted to the shaft 11a through the auxiliary spring17, and in addition to the unwinding spring force of the auxiliaryspring 17, the unwinding spring force of the main spring 18 rotates thereel 11 to retract and wind the belt 13 around the reel 11.

What is claimed is:
 1. A seat belt retracting and winding devicecomprising:a frame; a winding reel rotatably supported by said frame;spring means connected between said frame and said winding reel andincluding a main spring and an auxiliary spring; said winding reelwinding thereon a seat belt with a spring force of at least one of saidmain and auxiliary springs; a spur gear rotatably supported by saidwinding reel and operatively interposed between said main and auxiliarysprings; means for detecting a wound quantity of said seat belt disposedon said wound seat belt; a fixing gear for fixing said spur gear andbeing interlocked with said detecting means; and means mounting saidfixing gear for movement to releasably engage with said spur gear inresponse to said detecting means; said detecting means causing saidfixing gear to operate selectively under an engagement condition forpreventing rotation of said spur gear with said spur gear and adisengagement condition from said spur gear for allowing rotation ofsaid spur gear, thereby exerting smaller and larger spring forces,respectively, on said seat belt, whereby the winding force exerted onsaid seat belt is reduced when said spring means is operated under saidengagement condition.
 2. A device as in claim 1 wherein said detectingmeans includes a drum rotatably and detachably supported by a shaft ofsaid fixing gear, said drum being adapted to roll on said wound seatbelt around said winding reel during its retraction.